Refrigerant compressor

ABSTRACT

A valve plate includes a plurality of suction holes and a plurality of suction reed valves for opening and closing them. At least two of these suction reed valves have different natural frequencies. In this configuration, a natural frequency of one reed valve is larger. Therefore, even when an operation frequency is changed to a higher frequency, the compressor can suck a refrigerant gas into a cylinder efficiently without occurring delayed closing and reduction of a lift amount. Thus, refrigerating capacity and compression efficiency can be increased.

TECHNICAL FIELD

The present invention relates to an improvement in efficiency of ahermetic compressor used in freezer-refrigerators, and the like.

BACKGROUND ART

Recently, an improvement in efficiency of a hermetic compressor used infreezer-refrigerators, and the like, has been strongly demanded. In aconventional hermetic compressor, the suction efficiency is increasedby, for example, providing a valve device of a compression part with twoholes, and the compression efficiency is improved. Such a compressor isdisclosed in, for example, Japanese Patent Unexamined Publication No.H3-175174. Hereinafter, an example of a conventional hermetic compressoris described with reference to drawings.

FIG. 6 is a sectional view showing a conventional refrigerantcompressor; and FIG. 7 is an exploded perspective view showing a valveof a conventional refrigerant compressor. To a hermetic container 51, anoutlet port 52A that is one end of a suction tube 52 is connected.Another end of the suction tube 52 is connected to a piping at thelow-pressure side of a refrigerating cycle (not shown). A motor 53includes a stator 54 and a rotor 55, so as to drive a compression part56. Furthermore, refrigerating machine oil 57 is preserved in a bottomportion of the hermetic container 51. A coil spring 58 elasticallysupports the motor 53 and the compression part 56.

The compression part 56 includes a cylinder head 61, a cylinder block62, a valve plate 64, a suction reed valve 67, a piston 68, a connectingrod 70 and a suction muffler 30. The cylinder head 61 forms a suctionspace 61A and a discharge space 61B. The cylinder block 62 contains acylinder 63. The valve plate 64 has two suction holes 65 and twodischarge holes 66. The suction reed valve (hereinafter, referred to as“valve”) 67 has a deformation part 67A. The connecting rod 70 is linkedto an eccentric part 69A of a crank shaft 69. The suction muffler 30communicates to a suction space 61A via a communicating tube 30A and tothe suction hole 65 of the valve plate 64, and sucks a refrigerant gasfrom an inlet port 30B.

Hereinafter, an operation of the refrigerant compressor configured asmentioned above is described. Firstly, the motor 53 drives thecompression part 56, so that the piston 68 reciprocates in the cylinder63. A low temperature and low pressure refrigerant gas returning from anexternal refrigerating cycle (not shown) is firstly sucked into thehermetic container 51 from the suction tube 52. The refrigerant gas isfurther sucked from the inlet port 30B of the suction muffler 30 andpasses through the suction hole 65 via the communicating tube 30A.During the suction stroke, by flexing the deformation part 67A of thevalve 67, the refrigerant gas opens the valve 67 and is led to thecylinder 63. During the compression stroke, the valve 67 is closed.Thus, the refrigerant gas is compressed to high temperature and highpressure, passes from the discharge hole 66 through a discharge tube(not shown) and is led to the external refrigerating cycle (not shown)so as to be used for a refrigerating operation.

At this time, the valve 67 is so designed as to have a natural frequencyfor carrying out an opening and closing operation with good timing inaccordance with a low-speed operation frequency. Therefore, thecompressor is capable of operation with a reduced suction loss and ahigh volumetric efficiency.

However, when a low-speed operation frequency is changed to a high-speedoperation frequency due to the change in cooling load conditions, thetiming of opening and closing operation determined by the naturalfrequency of the valve 67 is off. At this time, even when the pressurein the cylinder 63 exceeds the pressure in the suction space 61A of thecylinder head 61, the valve 67 does not complete a closing operation.Consequently, delayed closing occurs, causing a backflow of arefrigerant gas, so that the volumetric efficiency is lowered and therefrigerating capacity and the refrigerating efficiency are lowered.

As a solution to reduce the backflow of a refrigerant gas due to delayedclosing of the valve 67, designing the valve 67 to have a high naturalfrequency in accordance with the high-speed operation is considered. Inthis case, since the spring constant of the deformation part 67A isincreased, an amount of flexure is reduced, so that the suction loss isincreased and accordingly the refrigerating capacity and therefrigerating efficiency are lowered.

SUMMARY OF THE INVENTION

The refrigerant compressor of the present invention includes a piston, acylinder and a valve plate. The valve plate is provided at an openingend of the cylinder and includes a plurality of suction holes. Therefrigerant compressor of the present invention further includes aplurality of suction reed valves, which is provided between the openingend of the cylinder and the valve plate, for opening and closing theplurality of suction holes, respectively. At least one of the suctionreed valves has a natural frequency different from that of the otherreed valves. With this configuration, even when an operation frequencyis changed, delayed closing of the suction reed valve and reduction inan amount of flexure are prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a refrigerant compressor in anembodiment of the preset invention.

FIG. 2 is a front view showing a suction reed valve of the refrigerantcompressor shown in FIG. 1.

FIG. 3 is a sectional view showing a cylinder head part of therefrigerant compressor shown in FIG. 1.

FIG. 4 is a graph showing a pressure in a cylinder and an amount offlexure of a reed valve in one stroke in a low-speed operation of arefrigerant compressor in an embodiment of the present invention.

FIG. 5 is a graph showing a pressure in a cylinder and an amount offlexure of a reed valve in one stroke in a high-speed operation of arefrigerant compressor in an embodiment of the present invention.

FIG. 6 is a sectional view showing a conventional refrigerantcompressor.

FIG. 7 is an exploded perspective view showing a valve of therefrigerant compressor of FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a sectional view showing a refrigerant compressor in anembodiment of the preset invention. FIG. 2 is a front view showing asuction reed valve. FIG. 3 is a sectional view showing a cylinder headpart.

To a hermetic container 1, an outlet port 2A that is one end of asuction tube 2 is connected. Another end of the suction tube 2 isconnected to a piping at the low-pressure side of a refrigerating cycle(not shown). A motor 3 includes a stator 4 and a rotor 5, and drives acompression part 6. Furthermore, refrigerating machine oil 7 ispreserved in a bottom portion of the hermetic container 1. A coil spring8 elastically supports the motor 3 and the compression part 6.

The compression part 6 includes a cylinder head 101, a cylinder block12, a valve plate 110, suction reed valves (hereinafter, referred to as“valve”) 120A and 120B, a piston 18, a connecting rod 20 and a suctionmuffler 130. The cylinder head 101 forms a suction space 101A and adischarge space 101B. The cylinder block 12 contains a cylinder 13. Theconnecting rod 20 is linked to an eccentric part 19A of a crank shaft19. The suction muffler 130 communicates to a suction space 101A via acommunicating tube 130A and to suction holes 112A and 112B of the valveplate 110, and sucks a refrigerant gas from an inlet port 130B.

The valve plate 110 has the suction holes 112A and 112B and dischargeholes (not shown). The suction holes 112A and 112B are respectivelyinclined from opening portions 114A and 114B of the valve plate 110 atthe side of the cylinder 13 to opening portions 114C and 114D of thevalve plate 110 at the side of cylinder head 101 in the direction inwhich a distance between the suction holes is reduced. The valves 120Aand 120B have deformation parts 122A and 122B having different lengthseach other, respectively. Since the deformation part 122A is longer thanthe deformation part 122B, the spring constant of the valve 120A issmaller, and the valve 120A has a lower natural frequency than that ofthe valve 120B. Furthermore, the shapes of the valves 120A and 120B areasymmetric with respect to centerlines 124A and 124B of the deformationparts 122A and 122B. Positions of center points of the suction holes112A and 112B correspond to points 126A and 126B of the valves 120A and120B, respectively.

Seal parts 128A and 128B seal the suction holes 112A and 112B providedon the valve plate 110.

Hereinafter, an operation of the refrigerant compressor configured asmentioned above is described. FIG. 4 is a graph showing a pressure in acylinder and an amount of flexure of a reed valve in one stroke in alow-speed operation of a refrigerant compressor in an embodiment of thepresent invention. FIG. 5 is a graph showing a pressure in a cylinderand an amount of flexure of a reed valve in one stroke in a high-speedoperation of a refrigerant compressor in an embodiment of the presentinvention.

The motor 3 drives the compression part 6, so that the piston 18reciprocates in the cylinder 13. A low temperature and low pressurerefrigerant gas returning from an external refrigerating cycle (notshown) is firstly sucked into the hermetic container 1 from the suctiontube 2. The refrigerant gas is further sucked from the inlet port 130Bof the suction muffler 130 and passes through the suction holes 112A and112B via the communicating tube 130A. During the suction stroke, byflexing the deformation parts 122A and 122B of the valves 120A and 120B,the refrigerant gas opens the valve 120A and 120B and is led to thecylinder 13. During the compression stroke, the valves 120A and 120B areclosed, and the refrigerant gas is compressed to high temperature andhigh pressure, passes from the discharge hole through a discharge tube(not shown) and is led to the external refrigerating cycle to be usedfor a refrigerating operation.

When the piston 18 reciprocates in the cylinder 13, in the suctionstroke, the piston 18 shifts to the side of a bottom dead center. In alow-speed operation, in this suction stroke, gas pressure load, which isgenerated by differential pressure when the pressure 140 in the cylinder13 becomes lower than the pressure in the suction space 101A of thecylinder head 101, acts on the valves 120A and 120B. At this time, at apoint 140A, the suction reed valves 120A and 120B start to open, and therefrigerant gas is sucked into the cylinder 13. The point 140A means apoint at which the gas pressure load generated by differential pressurebecomes larger than a resultant force of flexure load of the valves120A-120B and an adhesion force with the viscosity of refrigeratingmachine oil at the seal parts of the valves 120A-120B.

Furthermore, in the compression stroke, the valves 120A and 120B areclosed at a point 140B at which the pressure in the cylinder 13 exceedsthe pressure in the suction space 101A of the cylinder head 101, andsuction of the refrigerant gas from the suction muffler 130 iscompleted.

Between the point 140A and the point 140B, the valve 120A repeatsopening and closing operations 150A twice at a natural frequency inprimary deformation mode while flexing the deformation part 122A. Sincethe valve 120A is selected to have a natural frequency corresponding toa low-speed operation frequency, the valve 120A completes closingsubstantially with the same timing as the point 140B. Furthermore, sincethe spring constant of the valve 120A is small, even under conditionsthat the flow rate of sucked gas is slow during a low-speed operation, asuction loss due to the shortage of an amount of flexure is notincreased.

Furthermore, the valve 120B has a natural frequency and a springconstant higher than those of the valve 120A, and repeats opening andclosing operations 150B four times between the point 140A and the point140B. At this time, the valve 120B opens widely with a certain amount offlexure according to the circulation amount of refrigerant at the firstto third opening and closing operations 150B. At the fourth opening andclosing operation, since in the compression stroke, the differentialpressure between the pressure in the cylinder 13 and the pressure in thesuction space 101A of the cylinder head 101 is extremely small. At thistime, the refrigerant gas flows in the suction hole 112A of the valve120A that flexes more largely. Consequently, the amount of a refrigerantgas flowing in the suction hole 112B of the valve 120B becomes verysmall and the dynamic pressure by the flow of the refrigerant gas isreduced. That is to say, the valve 120B hardly flexes and it completesopening and closing operation near the point 141B.

Therefore, backflow of the refrigerant gas due to delayed closing of thevalves 120A and 120B is prevented, and the increase in suction loss dueto the shortage of the amount of flexure in the suction stroke is alsoprevented. As a result, the volumetric efficiency is increased.

Furthermore, in a high-speed operation, between the point 141A and thepoint 141B, the valve 120B repeats opening and closing operations 151Bthree times and flexes with a certain amount of flexure according to thecirculation amount of refrigerant, and then completes closing with goodtiming. The point 141A means a point at which the pressure in thecylinder 13 becomes lower than the pressure in the suction space 101A ofthe cylinder head 101. Furthermore, the point 141B means a point atwhich the pressure in the cylinder 13 exceeds the pressure in thesuction space 101A of the cylinder head 101.

The valve 120A opens widely in a certain amount of flexure according tothe circulation amount of refrigerant at the first opening and closingoperation 151A. On the other hand, in the second opening and closingoperation, since in a compression stroke, the differential pressurebetween the pressure in the cylinder 13 and the pressure in the suctionspace 101A of the cylinder head 101 is extremely small. Therefore, therefrigerant gas passes through the suction hole 112B of the valve 120Bthat flexes more largely. Consequently, the valve 120A hardly flexes andit completes the opening and closing operation near the point 141B.

Therefore, also in a high-speed operation, delayed closing or shortageof the amount of flexure of the valves 120A and 120B do not occur, sothat the refrigerant gas is sucked into the cylinder 13 efficiently.Consequently, in a case where the operation frequency is changed, therefrigerating capacity and the compression efficiency of the compressorare increased.

Furthermore, the shapes of the valves 120A and 120B are asymmetric withrespect to the centerlines 124A and 124B of the deformation parts 122Aand 122B. Therefore, working points 126A and 126B of the gas pressureload that act on the valves 120A and 120B deviate from centerlines 124Aand 124B of the flexing deformation of the valves 120A and 120B. Thus,the valves 120A and 120B start to open with torsion deformation. That isto say, torsional moment due to gas pressure load acts on the valves120A and 120B. Consequently, on one side of circular seal parts 128A and128B of the valves 120A and 120B, force for peeling off the adhesionportion with a viscosity of the refrigerating machine oil 7 isconcentrated, thus making it easy to open the valves 120A and 120B.Accordingly, in the suction stroke, the valves 120A and 120B start toopen earlier. Therefore, the refrigerant gas is sucked into the cylinder13 efficiently, and the refrigerating capacity and the compressionefficiency of the compressor are increased. Note here that in FIG. 2,both of the shapes of the valves 120A and 120B are asymmetric withrespect to the centerlines 124A and 124B of the deformation parts 122Aand 122B. However, they may be configured so that only one of the shapesis asymmetric.

A refrigerant gas inside the hermetic container 1 passes through thesuction space 101A in a high-temperature cylinder head 101 via thesuction muffler 130 and is sucked into the cylinder 13 from the suctionholes 112A and 112B provided on the valve plate 110. Herein, therefrigerant gas inside the cylinder 13 is in a high temperature state ofabout 100° C. by a compression action and is discharged to a dischargespace 101B of the cylinder head 101. Thus, the cylinder head 101 isheated to high temperature state of about 80° C.

In this case, as an interval between the two suction holes 112A and 112Bof the suction space 101A in the cylinder head 101, at least a distancecorresponding to a sum of the widths of the seal part 128A and the sealpart 128B is necessary. Herein, as shown in FIG. 3, in a case where thesuction holes 112A and 112B are inclined, it is not necessary toconsider the widths of the seal part 128A and the seal part 128B, and itis possible to greatly reduce the interval between the suction holes112A and 112B. Thus, the suction space 101A in the cylinder head 101 canbe configured to have a reduced volume and heat receiving area, so thatthe thermal transmission to the flowing refrigerant gas is reduced.Accordingly, the temperature of the refrigerant can be kept low, thedensity of the gas refrigerant increases and the circulation amount ofthe refrigerant increases. Consequently, the refrigerating capacity andthe compression efficiency of the compressor increase. Note here that inFIG. 3, both of the suction holes 112A and 112B are inclined, but onlyone of them may be inclined.

Note here that in the embodiment, the number of the valves 120A and 120Bis two. However, when the number is three or more, the same effect canbe obtained.

Furthermore, in the embodiment, the natural frequency is changed byvarying the lengths of the valves 120A and 120B. However, the sameeffect can be obtained even when the natural frequency is changed byvarying the widths or shapes of the valves 120A and 120B.

Furthermore, in the embodiment, the case where the number of opening andclosing operations in one stroke of the valve 120A and 120B is two tofour is described, however the same effect can be obtained when thenumber is one or more.

INDUSTRIAL APPLICABILITY

A refrigerant compressor of the present invention includes a piston, acylinder and a valve plate. The valve plate is provided at an openingend of the cylinder and has a plurality of suction holes. Therefrigerant compressor of the present invention further includes aplurality of suction reed valves provided between the opening end of thecylinder and the valve plate, and opens and closes the plurality ofsuction holes, respectively. At least one of the suction reed valves hasa natural frequency different from that of the other reed valves. Withthis configuration, since refrigerating capacity and compressionefficiency of the refrigerant compressor can be increased, therefrigerant compressor can be used for air conditioners,freezer-refrigerators, and the like.

1. A refrigerant compressor, comprising: a piston; a cylinder housingthe piston; a valve plate, which has a first suction hole and a secondsuction hole, provided at an opening end of the cylinder; a firstsuction reed valve, which opens and closes the first suction hole,provided between the opening end of the cylinder and the valve plate;and a second suction reed valve, which opens and closes the secondsuction hole and has a natural frequency different from that of thefirst reed valve, provided between the opening end of the cylinder andthe valve plate.
 2. The refrigerant compressor according to claim 1,wherein the first suction reed valve has a first deformation part andthe second suction reed valve has a second deformation part, at leastone of a shape of the first suction reed valve being asymmetric withrespect to a centerline of the first deformation part and a shape of thesecond suction reed valve being asymmetric with respect to a centerlineof the second deformation part.
 3. The refrigerant compressor accordingto claim 1, wherein at least one of the first suction hole and thesecond suction hole is inclined from an opening end face of the valveplate at the cylinder to another end face in the direction in which aninterval between the first suction hole and the second suction hole isreduced.